Positive retained actuation switch

ABSTRACT

A warning switch having a housing with a central cavity separated by a first piston and a second piston into a first chamber and a second chamber. The first chamber is connected to a first pressure and the second chamber is connected to a second pressure. The first and second pistons are separated by a stem with an annular land section. The land section is flanked by annular ramps leading to a cylindrical section on the stem. A non-conductive body having a cylindrical bore is secured to the housing. A plunger member with an axial projection is located in the cylindrical bore and extends into the central cavity to contact the land section on the stem. A clip having a plurality of prongs is attached to the rear of the axial projection. A pressure differential between the first and second chambers will move the first and second pistons toward the lower pressure chamber permitting the axial projection to move off the land section down the ramp to the cylindrical section on the stem. As the axial projection moves down the ramp in response to the resilient member, the clip engages the terminal to initiate an operational signal to a pressure differential indicator. Upon termination of the pressure differential, a resilient member holds the prongs in contact with the terminal until de-activated by equalized pressure in the first and second chambers returning the axial projection to the land section.

Ulliifid States Patent 1 Apple et al. 1 May 29, 1973 [54] POSITIVE RETAINED ACTUATION SWITCH 57 ABSTRACT [75] Inventors: Myron L. Apple; Harold W. Hughes, A warning switch having a housing with a central caviboth of Saint Joseph, Mich. ty separated by a first piston and a second piston into [73] Assignee: The Bendix Corporation, South a first chamber and a second chamber. The first Bend, Ind chamber is connected to a first pressure and the second chamber 1s connected to a second-pressure. [22] Filed: Dec. 13, 1971 The first and second pistons are separated by a stem with an annular land section. The land section is [21] Appl 207365 flanked by annular ramps leading to a cylindrical sec tion on the stern. A non-conductive body having a Cl 200/153 200/159 A cylindrical bore is secured to the housing. A plunger Int. member with an axial projection is located in the Field Of Search D, 61.19, cylindrical bore and extends into the entral cavity to 200/153 153 159 159 A contact the land section on the stem. A clip having a plurality of prongs is attached to the rear of the axial Refel'eflces Cited projection. A pressure differential between the first UNITED STATES PATENTS and second chambers will move the first and second pistons toward the lower pressure chamber permlttmg 3,606,487 9/1971 Kersting ..200/82 D X the axial projection to move off the land section down 3,637,963 l/l972 Wellman ..200/82 D the ramp to the cylindrical section on the stem. As the g l et 2 0 0}g axial projection moves down the ramp in response to i i er the resilient member, the cli en a es the terminal to 2,060,377 11/1936 Knodle ..200/159RX initiate an operational Signalpto agpgessure differential FOREIGN PATENTS OR APPLICATIONS indicator. Upon termination of the pressure differential, a resilient member holds the prongs in con- 578,032 6/1946 Great Britain ..200/159 R Primary Examiner-Robert K. Schaefer Assistant Examiner-Robert A. Vanderhye Attorney-Leo H. McCormick, Jr. and William N. Antonis tact with the terminal until de-activated by equalized pressure in the first and second chambers returning the axial projection to the land section.

2 Claims, 5 Drawing Figures Patented May 29, 1973 3 Sheets-Sheet 1 Patented May 29, 1973 3 Sheets-Sheet 2 NQI F iii 5 Sheets-Sheet 5 MMN POSITIVE RETAINED ACTUATION SWITCH BACKGROUND OF THE INVENTION Safety standards now require that the front and rear brakes be independently operated. A single split master cylinder with a primary piston pressurizing fluid for the front wheels and a secondary piston pressurizing fluid for the rear wheels is connected through a differential pressure warning switch. When pressurized fluid is supplied to the front and rear brakes, a plunger is held in a groove. If a failure should occur in either the front or rear brakes, a pressure differential will occur causing the plunger to slide up a ramp and close an electrical contact to-initiate a signal for warning the operator of a malfunction in the brake system. However, upon release of the brake pedal the plunger will again slide down the ramp to break the electrical circuit. Thus, a malfunction signal is only activated while the brakes are applied. Since it is likely that the vehicle operator might overlook the signal if the brakes are briefly applied, it is desirable to have a warning switch which will continue to operate continually after an initial failure has activated the switch until the failure is corrected.

SUMMARY OF THE INVENTION are present in the first and second hydraulic systems.

It is therefore the object of this invention to provide a braking system with a malfunction indicator which upon activation by a lower pressure in one side of a dual hydraulic system will remain activated until equalizing pressures are retained in both sides of the dual hydraulic system.

It is another object of this invention to provide a warning switch with resilient means which maintains electrical continuity with an indicator upon initial activation until reset by equalizing pressures.

These and other objects will be apparent from reading this specification and viewing the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view of a differentially operated fluid pressure switch means in a dual hydraulic braking system of an automotive vehicle.

FIG. 2 is a sectional view of the fluid pressure switch means with equalizing hydraulic pressure in both the front and rear brake systems with an electrical contact resiliently held on a non-conductive sleeveto interrupt electrical continuity between an indicator and the switch.

FIG. 3 is a sectional view of the electrical contact of FIG. 2 which is resiliently held on an electrical terminal during and after an initial pressure differential is present in the dual hydraulic braking system.

FIG. 4 is a sectional view of the preferred embodiment of the resiliently controlled contact means for transmission of an operation signal indicating a pressure differential in the dual braking system in an interrupted position.

FIG. 5 is a sectional view of a contact means of FIG. 4 in the activated position.

DETAILED DESCRIPTION OF THE PRESSURE SWITCH A master cylinder 10 of a type fully described in copending US. application Ser. No. 204,550, filed Dec. 3, l97l, and incorporated herein by reference has a primary pressurizing conduit 12 leading to an inlet port 14 and a secondary pressurizing conduit 18 leading to a second inlet port 20 of a pressure warning switch means 16. Fluid pressure in master cylinder 10 is developed by an operator initially depressing pedal 22 which causes a first hydraulic fluid pressure to be communicated through inlet port 14 via a metering valve means 24, see FIG. 2, (of a type fully described in US. Pat. No. 3,603,648 and incorporated herein by reference) positioned in the housing 26 of the warning switch 16. The metering valve 24 is connected to the front wheel disc brakes 28 through outlet ports 30 in the housing 26. Further depression of pedal 22 causes a second hydraulic fluid pressure to be transmitted through the second inlet port 20 to the cylindrical cavity 32 in housing 26 and past outlet port 34 to the rear wheel drum brakes 36.

With equalizing pressures in conduits I2 and 18, the warning switch 16 is inactivated and the electrical continuity between the grounded housing 26 and indicator light 38 interrupted. With a failure in either the connection between conduit 12'and the front wheel disc brakes 28 or the connection between conduit 18 and the rear wheel drum brakes 36, a pressure differential will be sensed by the warning switch means 16. Upon sensing a pressure differential, warning switch means 16 establishes electrical continuity between ground 40 through the housing 26 to cause indicator light 38 to be energized by electrical power source 42. Electrical continuity through the warning switch means 16' will continue until an equalizing pressure is restored in conduits 12 and 18. y

In more particular detail, the warning switch means 16 shown in FIG. 2 consists of housing 26 having a cylindrical cavity 32 therethrough. The cylindrical cavity 32 is connected to the first inlet port 14 by passage 44 and the second inlet port 20 by passage 46.

A first piston means 48 has a cylindrical section 50 with agroove 52 for holding seal 54 is located inthe cylindrical cavity 32. The cylindrical section 50 is located adjacent the first inlet port passage 44. The forward face 56 of the cylindrical section 50 forms a first chamber 58 with cap 60. Cap 60 retains the end 62 of the metering valve means 24 located in the first chamber 58. The first chamber 58 has outlet ports 30 going to the front wheel disc brakes 28.

A second piston means 60 has a cylindrical section 62 with a rib 64. A seal 66 located between discs 68 and 70 which surround the cylindricalsection 62 prevents hydraulic fluid under pressure from being communicated from a second chamber 72 into a control chamber 74 between the first and second piston means 48 and 60.

The second chamber 72 is formed by the forward face 76 of the second piston means 60 and plug 78 which seals the cylindrical cavity 32. Plug 78 has a central passage which permits communication of pressurized fluid from the second chamber'74 through outlet 34 to the rear wheel drum brakes 36.

The first piston 48 and second piston 60 are rigidly connected to each other by a stem means 80. The stem means 80 has a first cylindrical section 82 and a second cylindrical section 84 adjacent a first annular ramp 86 and a second annular ramp 88 leading to a first edge 90 and a second edge 92 of a land section 94, respectively.

An electrically non-conductive body or fitting 95 is secured in opening 96 of housing 26 by threads 98. The body 95 has a stepped cylindrical bore 100 along its central axis. A sleeve 102 which is concentric with the central axis of the stepped bore extends into a switching chamber 104 formed by non-conductive body 95 and the housing 26 at the bottom of opening 96.

An electrical terminal 106 has one end 108 located in the switching chamber 104 and another end 110 which extends into a connection chamber 112 of the non-conductive body 95. End 108 has a diameter substantially equal to sleeve 102 and is held in a tight abutting relationship therewith along the central axis of bore 100 by anchor 1 l3 spaced along the terminal 106. The anchors 113 are embedded in the non-conductive body 95. End llis connected to indicator 28 by electrical lead 115.

A plunger means 114 includes a cylindrical member 116 which has a diameter substantially equal to the section of the stepped bore 100. The cylindrical member 116 is retained in the bore 100 by arcuate rib 118 and includes an axial projection 120 which extends through an opening 123 of housing 26 and into the second chamber 74 of the cylindrical cavity 32. The axial projection 120 has a spherical head 122 which is brought into contact with the stem means 80 by a resilient means 124. The resilient means 124 is located in the switching chamber 104 with one end 126 against a shoulder 128 of the non-conductive body 94 and the other end 130 on the rear face 132 of the cylindrical body 116.

Contact clip means 134 has a base 136 which is centra'lly positioned on the rear face 132 of the cylindrical body 116 by rivet 138. A plurality of prong members 140 integral with the base 136 extend rearwardly on an inward angle for a predetermined distance to form a contact point 142. Each of the prong members has an arcuate segment 144 extending radially outwardly from the contact point 142.

MODE OF OPERATION OF THE PRESSURE SWITCH With substantially equal pressures developed in the master cylinder and transmitted to the first and second chambers 58 and 72, stern means 80 will remain centered as shown in FIG. 2. Spherical head 122 of the plunger means 114 will remain in contact with land 94. With the spherical head 122 on land 94, the prongs 140 will bias the contact points 142 against the nonmoves. With further movement of the stem means 80, spherical head 122 will be resiliently biased on the arcuate ramp 86. The biasing force of the resilient means 124 will be broken down into a horizontal force and a vertical force, the vertical force adding to the pressure force on the face 56 to further move the stern means 80 toward the second chamber 72.

When the combined moving forces of the resilient means 124 and fluid pressure in chamber 58 have moved the second piston means 60 and associated disc 68 and into abutment with the end 146 of plug 78, further movement is prevented since the plug acts as a limiting stop. In this position the spherical head 122 will be urged against the cylindrical section 82 of the stem means by resilient means 124. As the plunger means 114 moves the spherical head 122 down the arcuate ramp 86, the prongs of the clip means 134 will slide down the non-conductive sleeve 102 onto end 108 of the electrical terminal 106 to close the electrical circuit between the terminal 106 and the housing 26, see FIG. 3. When the electrical circuit is closed, an electrical operational signal will energize indicator 38 to visually inform the operator of a malfunction in the braking system.

Resilient means 124 will hold the second piston means 60 against stop 146 until the hydraulic pressure in chamber 72 acting on face 76 and disc 70 is great enough to overcome the hydraulic pressure in chamber 58 acting on face 56 and the resultant from the biasing force of the resilient means 124. When this holding force is overcome stem means 80 will slide in bore 32, causing the spherical head 122 to move the arcuate ramp 86 until positioned on land 94. Correspondingly, the contact points 142 of the prongs will slide off the end 108 of the electrical terminal onto the nonconductive sleeve 102, causing an electrical continuity between the housing 26 and the electrical terminal 106 to be broken. With electrical continuity broken, indicator 38 is deactivated informing the operator that equalized braking pressures are present in the first and second chambers 58 and 72.

When a malfunction occurs in the braking system causing a loss of fluid pressure in the first chamber 58, the fluid pressure in chamber 72 acting on face 76 will move face 56 of the first piston means 48 against stop 148. In this position the spherical head 122 will have moved down arcuate ramp 88 into the second cylindrical section 84 allowing the contact points 142 of the prong means 140 to engage end 108 (as shown in FIG. 3), of the electrical terminal 106 and establish electrical continuity with the housing 26. Similarly as stated above, the resilient means 124 will hold stem means 80 in this stationary position permitting continual electrical energization of the indicator 38 until sufficient hydraulic pressure in chamber 58 acting on face 56, which has a slightly larger diameter than face 76, to reposition land 94 under the spherical head 122.-

The sliding of the contacts 142 on and off the nonconductive sleeve and end 108 of terminal 106 will re- .duce the possibility of an oxide coating covering the contact points 142 after a period of time. Thus, the possibility of electrical discontinuity through corroded contacts is reduced since any build-up of oxide will essentially be wiped away through the sliding motions.

DESCRIPTION OF THE PREFERRED EMBODIMENT The invention as shown in FIG. 4 is essentiaLly the same as that of FIG. 2 with the exception of the means for establishing electrical continuity between terminal 106 and housing 26. It should be noted that parts that are identical to those used in FIG. 2 are given the same reference numeral since they perform the same function in this embodiment of FIG. 4.

A rearward axial projection 250 is secured to the rear of the cylindrical body or disc 116 and extends into the switching chamber 104 toward end 108 of the electrical terminal 106. A disc 252 having its periphery abutting shoulder 254 of the non-conductive body 95 has a plurality of prongs 256 extending inwardly on an angle for a predetermined distance. Each of the prongs has a contact point 258 from which an arcuate section 260 extends radially outward. When the spherical head 122 of the plunger means 114 is located on land 94, the head 262 of the cylindrical projection 250 will engage prongs 256.

When a pressure differential occurs between chambers 58 and 70, the first and second piston means 48 and 60 will move toward the chamber with the lower pressure. As the stem means 80 moves off center, spherical head 122 will slide off land section 94 down the ramp toward the cylindrical section of the stem means 80. correspondingly, as the plunger means 114 moves, head 262 will move away from the prongs thereby permitting the prongs to resiliently engage end 108, see FIG. 5. With contacts 258 engaged with end 108, electrical continuity between terminal 106 is established with housing 26 through resilient means 124. When electrical continuity is established, an electrical operational signal will be transmitted allowing electrical source 42 to activate indicator light 38. Resilient means 124 will hold the spherical head 122 in the cylindrical section of the stem means 80 until an equalizing pressure is present in chambers 58 and 70 at which time the spherical head will be moved up the arcuate ramp to the land section 94. Correspondingly, head 262 will engage and spread prongs 256 moving contacts 258 out of engagement with end 108 interrupting the operational signal to the indicator light 38.

We claim:

1. Switch means responsive to a pressure differential between a first and second hydraulically operated system, said switch means comprising:

a housing having a cylindrical cavity therein with a first inlet port and a second inlet port connected to separate fluid pressurizing means;

first piston means located in said cylindrical cavity adjacent said first inlet port for forming a first chamber in the cylindrical cavity with the housing, said first chamber having a first outlet port connected to said first hydraulically operated system;

second piston means located in said cylindrical cavity adjacent said second inlet port for forming a second chamber in the cylindrical cavity with the housing, said second chamber having a second outlet port connected to said second hydraulically operated system;

stem means located in said cylindrical cavity for connecting said-first piston means to said second piston means, said stem means being ofa smaller diameter than said first and second piston means, said stem means having a land section with a diameter substantially equal to said first and second piston means, said stem means having a first ramp going from a first cylindrical section of the stem to one edge of said land section and a second ramp going from a second cylindrical section of the stem to the other edge of said land section;

an electrical non-conductive body secured to said housing, said non-conductive body having a cylindrical bore therethrough;

an electrical terminal having one end fixed to said non-conductive body in said cylindrical bore and the other end connected to a pressure differential indicator for transmitting an operational signal;

plunger means located in said cylindrical bore having an axial projection with a spherical head on one end and a cylindrical head on the other end, said spherical head extending into said cylindrical cavity to contact said land section on said stem means when the hydraulic pressure in the first and second chamber acting on the first and second piston is substantially equal;

a first disc surrounding said axial projection, said first disc having a diameter substantially equal to said cylindrical bore, said axial projection being maintained in axial alignment in said cylindrical bore by the engagement of the periphery of said first disc with said cylindrical bore;

clip means having a second disc whose periphery abuts a shoulder in said cylindrical bore, said second disc having a plurality of prongs extending inwardly on an angle from the periphery, each of said prongs having an arcuate section extending radially outward at a predetermined distance from said disc; and

resilient means located in said cylinder bore between said first and second discs for biasing said spherical head of the plunger means into contact with said stem means and said second disc against said shoulder, said cylindrical head of the plunger means engaging said prongs when said spherical head is on said land section causing the prongs to pivot. on said shoulder to prevent the arcuate segments from contacting said one end of the electrical terminal, said cylindrical head moving out of engagement with said prongs as the spherical head moves down the arcuate ramp in response to a pressure differential between said first and second chambers causing the first and second piston means to slide in said cavity'permitting said prongs to contact said one end of the electrical terminal, said resilient means aiding said pressure differential in sliding said piston means in said cylindrical cavity when said spherical head is on one of said first and second ramps, said resilient means maintainingsaid clip means in contact with said electrical terminal and continually transmitting said operational signal therethrough until substantially equal pressures in the first and second chamber reposition said spherical head on said land section and thereby break the electrical continuity between the housing and the electrical terminal.

2. The switch means, as recited in claim 1 wherein said electrical terminal includes:

anchor means fixed in said electrical non-conductive body for holding the cylindrical head stationary. 

1. Switch means responsive to a pressure differential between a first and second hydraulically operated system, said switch means comprising: a housing having a cylindrical cavity therein with a first inlet port and a second inlet port connected to separate fluid pressurizing means; first piston means located in said cylindrical cavity adjacent said first inlet port for forming a first chamber in the cylindrical cavity with the housing, said first chamber having a first outlet port connected to said first hydraulically operated system; second piston means located in said cylindrical cavity adjacent said second inlet port for forming a second chamber in the cylindrical cavity with the housing, said second chamber having a second outlet port connected to said second hydraulically operated system; stem means located in said cylindrical cavity for connecting said first piston means to said second piston means, said stem means being of a smaller diameter than said first and second piston means, said stem means having a land section with a diameter substantially equal to said first and second piston means, said stem means having a first ramp going from a first cylindrical section of the stem to one edge of said land section and a second ramp going from a second cylindrical section of the stem to the other edge of said land section; an electrical non-conductive body secured to said housing, said non-conductive body having a cylindrical bore therethrough; an electrical terminal having one end fixed to said nonconductive body in said cylindrical bore and the other end connected to a pressure differential indicator for transmitting an operational signal; plunger means located in said cylindrical bore having an axial projection with a spherical head on one end and a cylindrical head on the other end, said spherical head extending into said cylindrical cavity to contact said land section on said stem means when the hydraulic pressure in the first and second chamber acting on the first and second piston is substantially equal; a first disc surrounding said axial projection, said first disc having a diameter substantially equal to said cylindrical bore, said axial projection being maintained in axial alignment in said cylindrical bore by the engagement of the periphery of said first disc with said cylindRical bore; clip means having a second disc whose periphery abuts a shoulder in said cylindrical bore, said second disc having a plurality of prongs extending inwardly on an angle from the periphery, each of said prongs having an arcuate section extending radially outward at a predetermined distance from said disc; and resilient means located in said cylinder bore between said first and second discs for biasing said spherical head of the plunger means into contact with said stem means and said second disc against said shoulder, said cylindrical head of the plunger means engaging said prongs when said spherical head is on said land section causing the prongs to pivot on said shoulder to prevent the arcuate segments from contacting said one end of the electrical terminal, said cylindrical head moving out of engagement with said prongs as the spherical head moves down the arcuate ramp in response to a pressure differential between said first and second chambers causing the first and second piston means to slide in said cavity permitting said prongs to contact said one end of the electrical terminal, said resilient means aiding said pressure differential in sliding said piston means in said cylindrical cavity when said spherical head is on one of said first and second ramps, said resilient means maintaining said clip means in contact with said electrical terminal and continually transmitting said operational signal therethrough until substantially equal pressures in the first and second chamber reposition said spherical head on said land section and thereby break the electrical continuity between the housing and the electrical terminal.
 2. The switch means, as recited in claim 1 wherein said electrical terminal includes: anchor means fixed in said electrical non-conductive body for holding the cylindrical head stationary. 